High-strength hot-formed steel sheet member

a technology of hot-formed steel and high-strength, which is applied in the direction of heat treatment equipment, manufacturing tools, furnaces, etc., can solve the problems of dimensional precision deterioration, increased springback and wall camber, and difficult production of complex product shapes, etc., and achieves delayed fracture resistance and high strength
US20170096724A1Active Publication Date: 2017-04-06NIPPON STEEL CORP
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
NIPPON STEEL CORP
Publication Date
2017-04-06

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Abstract

A high-strength hot-formed steel sheet member exhibiting both a consistent hardness and delayed-fracture resistance, and is characterized in that: the high-strength hot-formed steel sheet member has a prescribed chemical composition; the degree of Mn segregation α (=[maximum Mn concentration (mass %) at the sheet center in the thickness direction] / [average Mn concentration (mass %) at a depth of ¼ of the total thickness of the sheet from the surface]) is less than or equal to 1.6; the steel purity value as defined in JIS G 0555 (2003) is less than or equal to 0.08%; the average grain size for prior γ grains is less than or equal to 10 μm; and the number density of the residual carbides is less than or equal to 4×103 particles / mm2.
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Description

TECHNICAL FIELD

[0001] The present invention relates to a high strength hot formed steel sheet member, more particularly relates to a high strength hot formed steel sheet member excellent in delayed fracture resistance.BACKGROUND ART

[0002] In the field of steel sheets for automobile use, to achieve both lighter weight for improved fuel efficiency and improvement of the impact resistance, there has been growing use of high strength steel sheet having a high tensile strength. However, along with higher strength, the press formability of steel sheet falls, so production of complicated shapes of products has become difficult.

[0003] As a result, for example, along with the higher strength of steel sheet, the problem of the ductility falling and fracture occurring at portions with a high working degree and the problem of the springback and wall camber becoming greater and therefore the dimensional precision deteriorating arise. Therefore, it has not been easy to press-form steel sheet having ...

Claims

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